Insect and Disease Control
Organically Acceptabl Sprays for Mildews, Mites and Other Problems.
Apr 15, 2007
Integrated Pest Management (IPM) is the practice of applying many different forms of control to overcome garden damage by pests by the use of a variety of cultural practices. This article concentrates on available sprays that are approved for use in organic production. Mites, mildews, aphids, grubs, and caterpillars can infest and damage our valuable plants so sometimes we need an “off-the-shelf” product for insect control such as pyrethrum or rotenone.
Most allowed sprays are derived from an organic source – from something once living - but some simple inorganic chemicals are generally sanctioned. The article has three sections:
- Botanically B
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- s
- Biologically
- anically Based Products
Botanical pesticides are extracts from plants and tend not to remain in the environment for as long as synthetic chemicals. Because of this, more frequent spraying may be necessary. Those discussed are:
- Pyreth
- Normal">Derris
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- hrum
Perhaps the most widely used general-purpose insecticide is Pyrethrum an extract of the pyrethrum daisy. This general-purpose spray is used to control a wide variety of insects on flowers, fruit, and vegetables. A short list includes ants, aphids, caterpillars, earwigs, leafhoppers, thrips, and whitefly.
Pyrethrum will kill bees so should not be used until late afternoon when bees have left the garden. It is toxic for 12 hours.
The organic gardener should check the ingredients to ensure that the product does not contain piperonal butoxide, which is a prohibited chemical for organics.
Derris Dust.
Derris dust or Rotenone is extensively used to “dust” onto flowers and vegetables to control many pests: aphids, white butterflies, grubs, caterpillars, and potato moths. Derris remains toxic for 48 hours – wash vegetables carefully even after the withholding period.
As with Pyrethrum products, check the label because rotenone is often commercially adulterated with non-organic products.
Ryania Spray
Ryania from the plant (Ryania speciosa) may be available as quassia Chips.It is used to control codling moth, caterpillars, and beetles. Follow packet instructions.
(2) Simple Chemicals.
Oil Sprays.
Spray white oil on to fruit trees for scale, mites, codling moth, aphids, thrips, red spider, and white flies. Use with discretion – not on hot sunny days when the oil may burn the plant. In winter a heavier version is used, sometimes known as dormant (because the tree is dormant) oil. Oil coats the insect or eggs and suffocates them. Oil sprays can be made at home.
.
Bordeaux – copper mixtures.
Bordeaux, which has been used for centuries, is a mixture of copper sulphate (blue), and hydrated lime. A purist organic grower does not use the bought form, which has other ingredients but makes his own. Unlike the store bought, the home-made product must be used immediately as it cannot be stored.
Bordeaux is used to protect against bacterial and fungal problems in fruit, vegetables, and ornamentals. To make one bucket put 100 gm of the blue copper sulphate into half a bucket and 125 gm of lime into the other half. Stir both and mix.
A copper paste (copper sulphate and water) can be an effective cure for collar rot
Condy’s crystals (potassium permanganate)
30 gm of Condy’s crystals can be mixed with a bucket of water and sprayed onto plant foliage to control powdery mildew.
Sulphur and lime sulphur
Sulphur is an allowable product as a fungicide for the control of powdery mildew on vegetables and ornamentals, rust and various other fungal diseases on vegetables and ornamentals. Sulphur is an insecticide for various mites including those that attack citrus.
Sprinkle the brown sulphur powder on to zucchini and other squash to protect against mildew.
Sulphur is available as flowers of sulphur, wettable sulphur, or spraying sulphur. It should not be used in conjunction with an oil spray or on hot days.
Not all commercially available products are certified “organic” and the gardener should check the label.
Lime sulphur controls powdery mildew and some scale and mites on ornamentals. It is used as an insecticide on tomatoes and stone fruits.
The Queensland Department of Primary Industry cautions “Lime sulphur should not be applied when the air temperature is over 32 degrees Celsius, after a copper spray in the same season or within 2 weeks of an oil spray.”
(3) Biologically derived products
Bacteria
A naturally occurring bacterium (Bacillus thuringiensis) controls many grubs and caterpillar without affecting their predators. It comes as a powder that one mixes with water. In Australia it is bought as Dipel.
Diatomaceous earth
Diatomaceous earth is the fossilised remains of single celled organisms. Dusted on to susceptible soft bodied insects, including aphids, ants, slugs, and caterpillars, it kills by drying them out on contact. It is also an effective barrier for slugs.
Some pesticides may kill beneficial insects and so should be used with restraint for pest and disease control. Always follow label directions.
The copyright of the article Insect and Disease Control in Organic Gardens is owned by Phillip Richards. Permission to republish Insect and Disease Control in print or online must be granted by the author in writing.
